1. Field of the Invention
The present invention relates to dual-type gas generators for air bags used in air bag systems for automobiles.
2. Description of Related Art
So-called dual-type gas generators are used for the purpose of regulating the rate of inflation or the degree of tension of an air bag in response to, for example, the magnitude of the impact at a vehicle collision and the physique of the passenger.
In dual-type gas generators, two combustion chambers (gas generating portions) are independently operated to adjust the amount of gas generated and the discharging speed of that gas to an air bag. Such generators are sometimes susceptible to a situation in which, as a result of the ignition of the gas generating agent of one combustion chamber, the gas generating agent of the other combustion chamber is ignited. This constitutes a malfunction.
Although such a malfunction can be prevented by completely separating the two combustion chambers and the gas discharge passages, this solution results not only in an increase in the number of component parts but also an increase in the weight and the scale of the gas generator itself, which contrasts with the consumer demand for the compacting and weight-reduction thereof.
In U.S. Pat. No. 5,970,880, the combustion chambers are arranged in both ends of a housing, a safety valve 26 is provided in the right side combustion chamber to prevent the effect of the left side combustion chamber from transferring to the right side through a communication hole 6.
However, in order to ensure that the gas of the right side combustion chamber is discharged through the communication hole 6 to a central filter chamber and to prevent the gas from passing through the left side combustion chamber, the plate thickness of a section 28 and the width or plate thickness of a section 39 of the safety valve 26 should be adjusted and, depending on differences in an amount of a gas generating agent charged therein and a size of the communication hole 6, this should be re-adjusted.